Vibration called flutter or shimmy may occur in a rotating direction of a steering wheel such as due to wheel balance during the travel of a vehicle.
JP1994-206550A discloses a device configured to predict the occurrence of vibration of a steering wheel on the basis of detection values of axial forces of tie rods and prevent the occurrence of vibration of the steering wheel by driving an actuator of a vibration conversion mechanism substantially simultaneously with the occurrence of vibration of the steering wheel to supply oil in an accumulator to an oil chamber of a shaft.